The Department of Justice is investigating the Blue Bell ice cream company for its response to a listeria outbreak in April, 2015, that resulted in three deaths and at least 10 illnesses.

The Civil Division within the Department of Justice is investigating, among other things, whether the Texas-based company knew it was sending contaminated product to market, according to a source familiar with the probe. The investigation is in its early stages, the source told ABC News.

Blue Bell stopped production in April in order to retrain all employees and enhance preventative measures.

Affected by the listeria outbreak that killed three people and sent seven others to the hospital, Blue Bell Creameries announced that it will lay off 37 percent of its staff.

Blue Bell voluntarily recalled all products on April 20, 2015. It shut down operations to "embark on an intensive cleaning program" and begin a reboot on April 27. The Brenham, Texas-based company announced that this process is taking longer than expected, and it's not clear when production will resume. When it does, it will be limited and gradual.

"The agonizing decision to lay off hundreds of our great workers and reduce hours and pay for others was the most difficult one I have had to make in my time as Blue Bell's CEO and President," said Blue Bell Creameries CEO and President Paul Kruse.

"At Blue Bell, our employees are part of our family, and we did everything we could to keep people on our payroll for as long as possible. At the same time, we have an obligation to do what is necessary to bring Blue Bell back and ensure its viability in the future. This is a sad day for all of us at Blue Bell, and for me personally," he added.

The company said it will lay off 750 full-time and 700 part-time employees and furlough 1,400 others. The overall workforce had included 3,900 people.